1. Field o the Invention
This invention relates to a video signal reproducing apparatus for reproducing a video signal, and more particularly, to a video signal reproducing apparatus which is capable of reproducing a still picture by utilizing a memory.
2. Description of the Related Art
Conventional video signal recording and reproducing apparatuses such as video tape recorders (VTRs) are designed to reproduce still pictures using a field memory. More specifically, since ordinary TV systems adopt the interlaced scanning system, if a video signal corresponding to one field is written in the field memory and the signal stored in the memory is repeatedly read out without alterations, skew of 0.5 H (1 H representing 1 horizontal scanning period) may be generated at the end of each field. It has therefore been proposed to write in the field memory a reproduced video signal corresponding to 0.5 H consecutively following the writing of the video signal corresponding to one field and to continuously read out from the memory a video signal corresponding to the entire period (one field and 0.5 H period, which corresponds to 263 H period in the case of the NTSC system). This arrangement serves to eliminate generation of skew.
However, in the above-described conventional reproduction technique, one vertical scanning period (corresponding to 262.5 H in the NTSC system) of a video signal which is reproduced by a reproducing head during still picture reproduction differs from that (corresponding to 263 H in the NTSC system) of the video signal read out from the memory, thereby gradually generating a phase shift between the two video signals. This results in a very ugly picture in which a vertical synchronizing signal appears on the screen of the TV monitor, as shown in FIG. 1, when the operation mode is switched over from the still picture reproduction to the normal reproduction, and when the video signal sent to the TV monitor is changed over from the video signal read out from the field memory to that reproduced by the reproducing head, the vertical synchronizing signal being gradually removed from the screen by the response of the TV monitor thereafter (this phenomena being called page rolling).
In order to prevent the occurrence of such phenomena, U.S. Pat. application Ser. No. 209,491 filed on June 20, 1988 and assigned to the assignee of this invention proposes to alternately read out video signals conforming to the NTSC system and representing 263 H and 262 H. However, this arrangement requires a relatively large scale circuitry arrangement, and is not therefore suited to use in an inexpensive small-sized video tape recorder with a camera incorporated therein.